60 



Mr, Bolton was unable to give any clue to the manner in 

 which such remarkable sections as the above had obtained. 



The occurrence of the superficial deposits, as shown in 

 the foregoing section, is, I believe, to be explained by the 

 theory of glacial action, and is evidently a part of the great 

 change wrought upon the surface, by the agency of ice, 

 during the "glacial epoch"; coeval with the boulder drift. 

 The great ice sheet, which then covered all the north of 

 England, descended from the lake mountains, grinding 

 down the surface rocks, and depositing the clays and 

 gravels in its course. The evidence of this is most strik- 

 ingly displayed in the above section, each line of which 

 apparently marks out a period, and a pause, in its course. 



The iron ore occurring in these deposits is of a dark 

 colour, and of much lighter specific gravity than that from 

 the veins of limestone ; and it has the appearance of having 

 been all ground to powder. After exposure to atmospheric 

 influence it soon falls again into that state. The clays are 

 of a bright yellow colour, and of exceedingly fine grain, 

 being evidently the " flour of rocks," ground down by the 

 glacier in its passage over the clay-slates. The unfossilized 

 wood is in a remarkable state of preservation, occurring in 

 large fragments, as if it had been rudely broken up and 

 crushed, probably also by the ice. It is principally birch, 

 and some of the trees have been found of 2ft. diameter. In 

 one of the pits there was also a layer of peat, giving evidence 

 of a long period of rest and stagnation. 



The iron ore was thus, by glacial agency, transferred from 

 its original place of occurrence, from the outcrop of one reef 

 to another, and redeposited as drift; covered up by clays 

 and the debris of rocks, wherever there was a cavity to 

 receive it. The water resulting from the thaw of the ice 

 would carry the ore down with it into the crevices and 

 caverns of the limestone, where it is now found as soft or 

 " puddling" ore. Aggassiz points out in liis work on glaciers 



